The assignment of values to NPL's 1 kg standards following the third periodic verification of prototype kilograms.

The United Kingdom's national standard of mass, Kilogram 18, was assigned a value by BIPM in 1991 as part of the Third Periodic Verification of National Prototypes of the Kilogram. The assignment of values to other kilogram standards belonging to NPL, based on this value of Kilogram 18, is the first stage in disseminating the UK mass scale. The standards involved in this process and the measurements made on them are described in this report.